Does Google detect files in the WordPress plugin directory

by

It will, but why not go further and add a robots.txt?

# Google Image
User-agent: Googlebot-Image
Disallow:
Allow: /*

# Google AdSense
User-agent: Mediapartners-Google
Disallow:

# digg mirror
User-agent: duggmirror
Disallow: /

# global
User-agent: *
Disallow: /cgi-bin/
Disallow: /wp-admin/
Disallow: /wp-includes/
Disallow: /wp-content/plugins/
Disallow: /wp-content/cache/
Disallow: /wp-content/themes/
Disallow: /trackback/
Disallow: /feed/
Disallow: /comments/
Disallow: /category/*/*
Disallow: */trackback/
Disallow: */feed/
Disallow: */comments/
Disallow: /*?
Allow: /wp-content/uploads/